Method and apparatus for grinding and polishing surfaces



B. E. LUBOSHEZ Sept. 3,1946.

METHOD AND APPARATUS FOR GRINDING AND POLISHING SURFACES Filed June 25,1944 z e Y M W .m

W .Y. B .B.

Patented Sept. 3, 1946 UNITED STATES PATENT OFFICE METHOD ANDAPPARATUSFOR GRINDING AND POLISHING SURFACES Benjamin E. Luboshez, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N. Y.,

a corporation'of New Jersey Application June 23, 1944, Serial No.541,679

9 Claims. 1

The present invention relates to grinding and. polishing surfaces, andparticularly to a method and apparatus by the use of which a flatsurface can be obtained automatically with little or no individualadjustment by an operator.

In m copending patent application, Serial Number 537,410., 'iiled May26, 1944, I disclosed methods and apparatus for grinding and polishingsurfaces under conditions of uniform wear at all points on the surfaceandat the same time obtaining a regime of uniform Wear at all points onthe tool. The latter condition was achieved partly through the agency ofa separate com" pensatlng shoe working upon the tool.

The present invention is an "improvement on that disclosed in my abovenoted copending patent application. According to the present invention,conditions of uniform wear on all points of the Work and tool areachieved by a very simple machine involving only rotational movements,or their equivalent, and no auxiliary apparatus. The present inventionis intended primarily for the grinding and polishing 'of flat surfaces,such as the various faces of optical prisms' a ndflat plates of smalldimension (upt'o a few inches across), but the same is adapted forworking small lenses of shallow curvature.

One object of the present invention is to provide a method of grindingand polishing surfaces under conditions of uniform wear on all parts ofthe surface being worked and/or on all parts of the tool being used sothat no adjustment of parts is required by the operator during theoperation and the procedure is thereby rendered automatic. I

Another object of the present invention is to block the work in the formof an annulus, or ring, and bring it into surface contact with anarcuate or annular grinding surface in such a way that the surface toice-finished; is subjected to uniform Wear at all points when the blockof work is rotated.

And another object is to further dispose the block of work relative tothe annular grinding surface so that the tool is subjected to uniformwear as well as the work as the latter is rotated.

And a further object is to provide an apparatus for carrying out thisnovel methodand which apparatus is very simple and involves onlyrotational movements, or their equivalent, and no auxiliary apparatus.

And yet another object is to provide an apparatus which makes possiblethe production of' a large volume of work with the use of a singlegrinding tool.

The novel features that I consider characteristic of my invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its methods ofoperation, together with additional objects and advantages thereof, willbest be understood from the following descriptionof specific embodimentswhenread in connection with the accompanying drawing in which,

Fig. 1 is an enlarged diagrammatic View showing an annular surface ofwork engaging a portion of an annular grinding surface, in accordancewith the present invention, and used to prove that, with such a givendisposition of the two parts, when the work is rotated about its centerrelative to the tool, all points on the work and/or all points on thetool are subject touniform wear,

Fig. 2 is a diagrammatic plan view showing how the parts can be disposedso that a single tool can be utilized to grind six blocksof work,

Fig. 3 is a vertical section of a preferred embodiment "of blocking toolused in the present apparatus, and V k Fig. 4 is a side elevation, on areduced scale, of acomplete machine constructed in accordance withthepresent invention. For the sake of clarity and simplicity, onlytwoblocks of work have beenshown engaging the tool in diametricallydisposed relationship on the tool, rather than six as shown in Fig. 3,but it is pointed out that the drive of the machine is capable ofhandling as many blocks of work as the circumference of the tool willallow.

Like reference charaters refer to corresponding parts throughout thedrawing.

, In accordance with the present invention, if the job at hand is topolish a given face on a plurality of elements, such as optical prisms,a number of the prisms or elements are mounted on .a block in side byside relation in a circle so that the several surfaces to be ground andpolished lie substantially in a common plane and form a substantiallycontinuous annulus of work. As shown in Fig. 3, a suitable block In ofthe work may comprise a disk member having the edge deformed to providea trough or prism seat I I extending completely around the disk adjacentthe periphery thereof and concentric with the center. If the elements tobe worked are prisms, a plurality of them, two being shown in Fig. 3 atP, are mounted in side-by-side relation in the trough by means ofcement, plaster of Paris, etc., l2 with the surface of each to be groundlying substantially in a common plane X which is spaced from the lowerface of the block. The blocking step can be accomplished in a well-knownmanner by first placing a quantity of the cement in the trough and,after placing the prisms therein, pressing the surfaces of the prism tobe worked against a plane surface. When the elements of work are somounted in the block, the surface of each to be finished join to form asubstantially continuous surface of annular configuration which might becalled an annulus of work.

The back of the block II] is provided at its center with a boss i3 whichconstitutes a socket to receive the ball end M on a vertical spindle l5which is adapted to be rotated in a manner later described. The ball I 4has a horizontal pin [6 extending therethrough which engagescorresponding slots or openings in the socket so that the spindle canrotate the block l0 and at the same time the block is free to pivotrelative thereto in one direction if necessary.

One or more of such blocks of work, or assembly of optical parts, isarranged to rotate rapidly and press upon a large fiat annular tool 11.In practice, the tool is a circular disk with a raised annular region I8which constitutes the grinding surface. The block of work is mountedrelative to the tool as diagrammatically shown in Fig. 1 wherein only anarcuate portion of the tool is shown engaged by one block of Work.Considering only an arcuate portion of the tool engaged by one block,the grinding surface constitutes an elongated surface which is longerthan it is wide and the width of which is less than the diameter of theannulus of work.

As shown in Fig. 1, the block of work is mounted above the tool so thatthe annulus of Work extends across the width of the grinding surface,and there are two arcuate areas of contact (prts) and (p'r't's') betweenthe grinding surface and the annulusof work which are oppositelydisposed on the annulus of work or disposed circumferentially of thegrinding surface. In Fig. 1, the entire blocking tool is not shown, butonly a ring W is shown representing the annulus of work in order topoint out what disposition of the work and grinding surface is requiredto obtain uniform wear on the tool and work in accordance with thepresent invention. The shaded areas (Prts) and (p'r't's') represent theareas of the work and tool which are mutually in contact, and it isassumed that the whole area of the annulus of work W represents thesurface being ground or polished. This condition can only beapproximately real zed in practice, but in any case, whatever errors areintroduced affect the wear on the tool and not the wear on the work.

Consider the case when the annulus of work W is rotated about its centerQ when the tool I! is stationary, or the work is rotated suflicientlyrapidly so that if the tool is rotated slowly, for the purposehereinafter set forth, the motion of the grinding surface can beneglected. Under these conditions, it is clear that the wear at allpoints on the annulus W will be constant provided that all arcsconcentric with the center Q of the annulus in the areas of mutualcontact, such as (ps), (rt), (ps'), and (r't) are of constant length,since these arcs represent the amount of grinding surface I8 that anypoint on the annulus W passes over. Consequently the annulus of work andthe grinding surface are so mounted relative to one another that thisspecified condition exists. Since the tool I! is stationary, or itsangular speed compared to that of W is negligible, only the possibilityof unequal Wear 4 along radial lines on W need be considered an wearalong the circumferential lines would in any case average out.

The wear upon the grinding surface l8 along circles having 0 as a centerneed not be uniform since any such differences average out. However, anydifferences in wear in a radial direction cannot average out and must beconsidered in order to obtain uniform wear on the tool as well as on thework. In this case, the condition for uniform wear on the tool is thatall ends of the arcuate areas of mutual contact such as (pr) (st), (pr),and (st') divided by their respective distances from the center 0 of thetool must be constant, i. e. (pr)-:-(b)=(st)-:-(a). The annulus of workW and the grinding surface II are arranged relative to one another sothat these specified relations exist.

So far, it has been assumed that the pressure is applied between thegrinding surface I8 and the annulus of work W in a uniform manner, andthis is only possible if pressure is applied over the center of gravityof the shaded areas (prts) and (pr'ts') in the diagram. This applicationof pressure is obtained in the present instance by applying pressure tothe block of work through the spindle [5 to the ball-and-socket jointl3, l4, which is located at the center of the block.

Three conditions must, therefore, be realized in order to attain uniformwearing conditions on both the tool and the work, and the parts of thepresent apparatus are so dimensioned and relatively arranged as to makethese conditions existant. For example:

Q is the center of gravity of the shaded areas (prts) and (p'r't's).

These conditions are easily attainable in practice by empirical trial.The following proportions (referring to Fig. 1) are given by way ofexample as fulfilling all the requirements and permitting the use of sixspindle and block assemblies on one annular grinding surface,

(a) =9.1 (b) =l4.1 (c) =11 ((1) =4 (1) =5 While theoretically,conditions of uniform wear on the work and tool depend on the grindingsurface being stationary, in practical operation it is not feasible tokeep the grinding surface stationary because the grinding action thereonby the work would be repetitive and arcuate grooves would be worntherein. It is, therefore, necessary, from a practical standpoint, tomove the grinding surface relative to the Work in order, not only tomake the wear thereon nonrepetitive, but also in order to distribute theabrasive uniformly. If the tool is rotated very slowly, say one-half R.P. M., or very slow relative to the rotation of the work, there will beinsuflicient grinding action on the work due to such movement to upsetthe specified conditions of uniform wear on the parts and the life ofthe tool will be greatly increased due to the fact that the grindingaction of the work on the tool will be rendered nonrepetitive.

The present invention is conducive to greatly increased production permachine, or per grinding tool. In Fig. 2 I have shown how six blocks IDof work may be simultaneously ground and polished onza single tool I!havlngan-annular grinding surface I8. In a practical form of'themachine, six-vertical power driven spindles are arranged above arotatable turn-table in the-manner similar to a multiple-spindlevertical drill press. The number of blocks of work which can behandledby a. single tool is limited only by the relative diameters ofthe block and the annular grinding surface.

In Fig. 4 I have shownone embodiment of a complete machine for carryingout the present invention. For purposes of clarity, in this machine onlytwo blocks of work have been shown diametrically disposed on the annulargrinding tool, although it will be readily appreciated that the samedrive could be used for the six spindle machine illustrated in Fig. 2.The machine comprises aframe including a base 2|, an upright 22, and anarm 23 extending from the upright 22 in vertical spaced relation withthe base 2|. A tool I! having an annular fiat grinding surface It isrotatably mounted on the base 2| by having a conical post 24, extendingfrom the bottom thereof, engaging a conical bearing 25 on the base.

Rotatably and slidably mounted in bearings in the arm 23 are a pair-ofvertical spindles 15 on the lower nds of which blocks I!) of work areconnected in the manner shown in Fig. 3. The

blocks of work are like that illustrated in Fig. 3'

and oneof each is disposed relative to the grinding surface in therelationship shown in Fig. 1. Each block of work I0 is pressed againstthe an nular grinding surface by weights M slidably mountedon the top ofthe spindle and supported thereon by a flange 26 fixed to the spindle.

For rapidly rotating the blocks of work and very slowly rotating theannular grinding surface the following drive may be provided. The powerdriven shaft 28 is connected to a relatively large and centrally locatedspur gear 29 through bevel gears 3| .and 3|. This large spur gear is inturn in mesh with a small pinion 30 fixed to each of the spindles 15,the pinions being long enough to permit the spindles to be raised andlowered without disengaging the gears. If the drive shaft 23 is rotatedat 10 R. P. M. then the gearing shown to the blocks of work will permitsaid blocks to be rotated at approximately 60 R. P. M. which is theconventional grinding o polishing speed.

For obtaining a very slow rotation of the annular grinding surface toprevent nonrepetitive grinding action thereon the following drivetherefor may be provided. A small sprocket 32 is fixed to the driveshaft 28 to the left of thejupright 22 and is connected to a largersprocket 33 by a chain 34. The sprocket 33 drives a small bevel gear 35which meshes with a lar e bevel gear 38 formed on, or fastened to, theunder side of the tool I1. With this drive, it is possible to obtain a/2 R. P. M. of the tool with a 10 R. P. M. of the driving shaft, andwhich speed is slow enough so as not to upset the specified conditionsof uniform wearon-the work and grinding surface, but is sufiicient toprevent a nonrepetitive grinding action on the grinding surface.

As will be apparent from an inspection of Fig. 1, if only one or twoblocks of work are to be used the grinding surface need not be acomplete annulus but need only be an arcuate section sufiiciently longto extend clear across the block, or blocks,

terbeneath the :work rather than beinggiven a complete rotationalmovement.

It is-believed that it-will be obvious to those skilled in theart thatthe present method and apparatus for grinding andpolishing, by virtue ofthe conditions of uniform wear on the work and/or on tool obtainable bythe use thereof, is conducive to automatic operation and does away withthe need of skilled operators. No adjustments of the tool and/ or workby the operator is necessary, and which adjustments have been re quiredwith conventional grinding and polishing procedures and have demanded anexperienced operator, due to the prevailing conditions of uniform wear.The only thing which might require an operator would be the periodicapplication of of work to be surfaced. In this case the grinding surfacewould then be oscillated about its cenan abrasive and/or lubricant tothe work, and

even this step can be automatically accomplished the precise details andconstruction shown and described but is intended to cover allmodifications coming within the scope of the appended claims.

Having thus described my invention, what I claim is new and desire tosecure by Letters Patent of the United States is:

'l. The method of abrading a surface on a plurality of members under acondition of uniform Wear on all surfaces by the use of a grinding toolhaving a grinding surface which longer than it is wide, and comprisingthe steps of blocking the members so that the surfaces thereof to beworked form a substantially continuous and plane surface inthe form ofan annulus, the inner diameter of which is greater than the width ofsaid grinding tool; disposing the said annulus of work relative to thetool so that when the two are brought into surface contact the annulusof work will extend across the Width of. the tool and will have twooppositely disposed arcuate areas in contact therewith at any instant,the disposition of the annulus relative to the tool also being such thatthe lengths of all arcs concentric with the center of said annulus insaid arcuate areas are of equal length; forcing the tool and annulus ofwork together in such a way that the pressure per unit area is equalover the areas of the twcin contact; and rotating saidv annulus of workabout its own center relative to the tool.

2. The method of abrading a surface on a plurality of members by the useof a grinding tool having an arcuate plane grindingsurface which islonger than it is wide and under conditions of uniform wear on allsurfaces being ground and on the surface of the tool, and comprising thesteps of blocking the members so that the surfaces thereof to be workedform a substantially continuous and plane surface in the form of anannulus, the inner diameter of which is greater than the width ofsaiclgrinding surface; disposing said annulus of work relative to thetool so that when the two are brought into surface contact the annulusof Work will extend across the width of the grinding surface and willhave two oppositely disposed arcuate areas in contact therewith at anyinstant, the disposition of the annulus relative to the tool also beingsuch that the lengths of all arcs concentric with the center of saidannulus in said arcuate areas are of equal length, and the ratio of thewidth of each end of said arcuate areas to the radius of the grindingsurface to that end will be equal to one another; forcing the tool andannulus of work and said grinding surface together in such a way thatthe pressure per unit area is equal over the arcuate areas of the two incontact; and rotating said annulus of work about its own center relativeto the grinding surface.

3. The method according to claim 2, and including the step ofcontinuously rotating the grinding surface about its center relative tothe annulus of work at a very slow speed relative to the speed ofrotation of the annulus of work in order to provide a nonrepetitivegrinding action on the grinding surface by the work.

4. A grinding and polishing apparatus comprising in combination a toolhaving a grinding surface which is longer than it is wide; a blockingmember adapted for blocking a plurality of elements in side by siderelation with thesurface of each element to be worked lyingsubstantially in a common plane and constituting a substantiallycontinuous annular surface the inner diameter of which is greater thanthe width of the grinding surface; means for mounting said blockingmember relative to said tool so that said annular surface extends acrossthe width of said grinding surface and is adapted to contact the same intwo oppositely disposed arcuate areas each and every arc thereof whichis concentric with the center of said annular surface being of equallength; means for applying a pressure to the blocking member to forcesaid annular surface against said grinding surface, said means disposedso that the pressure per unit area between the grinding surface and saidannular surface is equal over the entire areas of the two in contact atany instant; and means for rotating said blocking member relative tosaid tool about an axis which is at the center of said annular surface.

5. An apparatus according to claim 4, inwhich the grinding surface ofthe tool is arcuate in shape, and in which the block is further so (115-posed that the ratio of the width of each end of said arcuate areas ofcontact to the radius of the grinding surface to said respective ends isequal one to the other, whereby a uniform wear is obtained on the toolas well as on the surfaces being abraded.

6. An apparatus according to claim 4, in which the grinding surface ofthe tool is arcuate in shape, and in which the block is further sodisposed that the ratio of thgwidth of each end of said arcuate areas ofcontact to the radius of the grinding surface to said respective ends isequal one to the other, whereby a uniform wear is obtained on the toolas well as on the surfaces being abraded; and means for moving said toolso that the grinding surface rotates very slowly about its center inorder that the grinding action on said surface by the work. will benonrepetitive, the speed of movement of said surface relative to thespeed of the work being small enough so that the conditions of equalwear on the surface and work due to the disposition of the two is notupset.

'7. A grinding and polishing apparatus comprising in combination a toolhaving an annular grinding surface of substantially large diameter; aplurality of blocking members, each adapted for blocking a plurality ofelements in side by side relation with the surface of each element to beworked lying substantially in a common plane and constituting asubstantially continuous annular surface the inner diameter of which isgreater than the width of the grinding surface; means for mounting saidblocking members in circumferentially spaced relation about saidgrinding surface so that the annular surface of work on each extendsacross the width of said grinding surface and. is adapted to contact thesame in two oppositely disposed arcuate areas each and every arc thereofwhich is concentric with the center of said annular surface being ofequal length and so that the ratio of the width of each end of saidarcuate areas of contact to the radius of the grinding surface to saidrespective ends is equal one to the other; means of applying pressure tothe blocking members so that the pressure per unit area between thegrinding surface and said annular surfaces is equal over the entireareas of contact at any instant; and means for rotating each of saidblocking members relative to said grinding surface about an axis whichis the center of the annular surface mounted thereon.

8. An apparatus according to claim 7 in which each blocking membercomprises a disc provided on one face with a circular recess concentricwith the periphery of the disc and in which the elements to be groundare adapted to be seated in side by side relation with the surface ofeach to be ground extending beyond the face of the disc and lyingsubstantially in a common plane and thereby form a substantiallycontinuous surface to be worked which is annular in shape.

9. A blocking member for blocking a plurality of elements, a planesurface of each of which is to be abraded, an comprising a disc having aface lying in a' plane; said face provided with an annular recessconcentric with the center of said disc and in which a plurality ofelements to be abraded are adapted to be fixedly mounted in side-by-sideand substantially abutting relation with the surface of each element tobe abraded lying substantially in a common plane, said surfaces jointlyconstituting a substantially continuous surface of annularconfiguration; and a socket fixed to the center of the face of said discopposite that face provided with said recess and adapted to receive aball end on a pressure transmitting and driving spindle, whereby thepressure per unit area between the surface of the work blocked on saiddisc and a grinding plane will be equal over the entire area of contactbetween the work and grinding surface.

BENJAMIN E. LUBOSHEZ.

